It said people faced serious health threats because of the toxic material.

The waste was dumped by a ship several weeks ago in unclear circumstances.

Trafigura Beheer BV, the company that chartered the ship Probo Koala, said it was very concerned by reports that "residue from the petrol cargo" had been disposed of inappropriately.

Those affected are being treated for stomach problems, nosebleeds and respiratory illnesses.

A senior aide to the prime minister told the BBC that Mr Konan Banny felt that people at the highest level should face the consequences.

Breathing problems

"I'm feeling very bad in the throat and I have headaches and I cannot breathe properly," Eric, a patient seeking treatment at Abidjan's university teaching hospital city, told the BBC's Focus on Africa programme.

The hospital has set up a specialist unit to deal with those suffering from similar symptoms.

"We don't know what we're treating. When they have stinging eyes or noses we give them drops. We want to know what it is so we know how to treat it," the manager of a local hospital told Reuters news agency.

He added the hospital was running low on some medicines and X-ray film.

In a statement, Trafigura Beheer BV said it told Ivorian authorities of the nature of the waste including "a written request that it should be safely disposed of, according to country laws".

"Trafigura can confirm that the residue (slops) were a mixture of gasoline, water and caustic washings," the statement continued.